Low light focus assist - Mamiya Universal

[igorxa]

I have a pair of Universal bodies, and I love using my 100mm f/2.8 with the Fuji FP-3000b in dark places, but I have the hardest time focusing. And I'm talking really dark. 1/4, f/2.8 ISO 3200. I can hand hold pretty well at that speed, especially if I use a flash and I just need the shutter for good ambient balance. The problem is focusing in light that low. I've tried the tape over the viewfinder trick, and it just doesn't work that well. After my local shop guy had a Super Speed Graphic on loan, I learned about its built in range finder assist, and after googling, I found out about the Kalart Focuspot, both of which supposedly make focusing in really low light very easy. I'm really confused on how it works. Can someone explain it to me? And would something like this be possible on the Mamiya? One of my rangefinders is a little off at infinity and unable to be adjusted (stripped and jammed screws), and eventually I'm going to turn that body into a wide angle flat top, so I figure it's a perfect guinea pig for some rf light experiments. Suggestions?

 

[shadowfox]

If your subject is within walking distance, have him/her hold a tiny LED light (that's LED, *not* Laser !!!). If your subject is not a person, tape the LED light to it.

Now you can use the rangefinder to match the LED light, approximately where your subject is.

The Kalart Focuspot uses the same technique but the light comes from the reverse direction.

 

[oftheherd]

If your subject is within walking distance, have him/her hold a tiny LED light (that's LED, *not* Laser !!!). If your subject is not a person, tape the LED light to it.

Or to the top of the camera, with an easy mechanism to turn it on and off. And no, I don't have a suggestion for that.

Now you can use the rangefinder to match the LED light, approximately where your subject is.

The Kalart Focuspot uses the same technique but the light comes from the reverse direction.

Ten characters.

 

[sevo]

Rangefinders work either way - if the camera is focused, rays from the subject across both mirrors meet at the viewing plane, and inversely the rays from a lamp at the viewing plane will also meet at the subject.

Later, advanced Kalart Focuspot models replaced part of the rangefinder, and allowed for using the rangefinder during operation. The basic Kalart (as used by Weegee and his generation) essentially was a eyepiece attached small flashlight (driven from the flash trigger battery) - the same can easily be imitated on any rangefinder camera by centrally mounting a laser pointer or focused LED torch into a small tube that fits the eyepiece.

 

[t6un]

Or one could fix a laser pointer to camera's accessory shoe, that way the possible aberrations of the complex viewfinder don't blur the laser spot(s). But the Kalart's way is cool because it also works when shooting from the hip or with any otherwise uncoupled viewfinder. I would use the laser in proximity of people with great care only. And no more than 5 mW.
Overall, I think a bright collimated flashlight in a hotshoe is a better idea.

 

[igorxa]

Rangefinders work either way - if the camera is focused, rays from the subject across both mirrors meet at the viewing plane, and inversely the rays from a lamp at the viewing plane will also meet at the subject.

Later, advanced Kalart Focuspot models replaced part of the rangefinder, and allowed for using the rangefinder during operation. The basic Kalart (as used by Weegee and his generation) essentially was a eyepiece attached small flashlight (driven from the flash trigger battery) - the same can easily be imitated on any rangefinder camera by centrally mounting a laser pointer or focused LED torch into a small tube that fits the eyepiece.

Can you explain to me what they did differently to make the rangefinder useable during operation?